We describe experiments on trapping of atoms in microscopic magneto-optical traps on an optically transparent permanent-magnet atom chip. The chip is made of magnetically hard ferrite-garnet material deposited on a dielectric substrate. The confining magnetic fields are produced by miniature magnetized patterns recorded in the film by magneto-optical techniques. We trap Rb atoms on these structures by applying three crossed pairs of counter-propagating laser beams in the conventional magneto-optical trapping (MOT) geometry. We demonstrate the flexibility of the concept in creation and in-situ modification of the trapping geometries through several experiments.
We demonstrate the possibility of trapping about one hundred million rubidium atoms in a magneto-optical trap with several of the beams passing through a transparent atom chip mounted on a vacuum cell wall. The chip is made of a gold microcircuit deposited on a silicon carbide substrate, with favorable thermal conductivity. We show how a retro-reflected configuration can efficiently address the chip birefringence issues, allowing atom trapping at arbitrary distances from the chip. We also demonstrate detection through the chip, granting a large numerical aperture. This configuration is compared to other atom chip devices, and some possible applications are discussed.
Three dimensional electrodynamic trapping of neutral atoms has been demonstrated. By applying time-varying inhomogeneous electric fields with micron-sized electrodes, nearly $10^2$ strontium atoms in the $^1S_0$ state have been trapped with a lifetime of 80 ms. In order to design the electrodes, we numerically analyzed the electric field and simulated atomic trajectories in the trap, which showed reasonable agreement with the experiment.
We experimentally demonstrate optical spectroscopy of magnetically trapped atoms on an atom chip. High resolution optical spectra of individual trapped clouds are recorded within a few hundred milliseconds. Detection sensitivities close to the single atom level are obtained by photoionization of the excited atoms and subsequent ion detection with a channel electron multiplier. Temperature and decay rates of the trapped atomic cloud can be monitored in real time for several seconds with only little detection losses. The spectrometer can be used for investigations of ultracold atomic mixtures and for the development of interferometric quantum sensors on atom chips.
Detecting single atoms (qubits) is a key requirement for implementing quantum information processing on an atom chip. The detector should ideally be integrated on the chip. Here we present and compare different methods capable of detecting neutral atoms on an atom chip. After a short introduction to fluorescence and absorption detection we discuss cavity enhanced detection of single atoms. In particular we concentrate on optical fiber based detectors such as fiber cavities and tapered fiber dipole traps. We discuss the various constraints in building such detectors in detail along with the current implementations on atom chips. Results from experimental tests of fiber integration are also described. In addition we present a pilot experiment for atom detection using a concentric cavity to verify the required scaling.
We present a permanent magnetic film atom chip based on perpendicularly magnetized TbGdFeCo films. This chip routinely produces a Bose-Einstein condensate (BEC) of 10^5 87Rb atoms using the magnetic film potential. Fragmentation observed near the film surface provides unique opportunities to study BEC in a disordered potential. We show this potential can be used to simultaneously produce multiple spatially separated condensates. We exploit part of this potential to realize a time-dependent double well system for splitting a condensate.